Renal disease is present in over half the patients with multiple myeloma, and Bence Jones proteins (BJP) appear to be directly responsible for a number of tubular, clinical and morphologic manifestations. It appears that certain physicochemical properties of BJP play a role in the tubulotoxicity of BJ proteins. This investigator proposes to study: 1. Whether only Kappa light chains are responsible for intra-cellular crystal formation in proximal tubular cells? 2. Whether variation in the net electric charge of BJ Proteins determine their tubolotoxicity, as well as the type of tubular injury produced? Light chains of variable isoelectric points (PI) as monomers and dimers will be injected intraperitoneally into rats. Sequential renal biopsies will be studied by light, immunofluorescent and electron microscopy. Tubular glycocalyx will be studied by light and electron microscopy, after colloidal iron staining. In addition, urinary pH, protein and glucose analysis and serum creatinine and BUN will be determined in order to clearly define some of the altered tubular functions.